The Sound of Evolution
Butorphanol
Mechanism of action:
Butorphanol is an opioid with κ-opioid receptor agonist activity and partial antagonist or weak agonist activity at the μ-opioid receptor. Its primary activity is at the κ-opioid receptor, where it suppresses pain signal transmission in the brain and spinal cord. It also inhibits calcium entry into nerve terminals, reducing the release of neurotransmitters such as substance P and glutamate. Its relatively weak μ-opioid receptor activity limits μ-receptor-related effects.
Reference(s):
1. Gear RW et al. (1999). The kappa opioid nalbuphine produces gender- and dose-dependent analgesia and antianalgesia in patients with postoperative pain. Pain.
2. Fan LW et al. (2002). Withdrawal from dependence upon butorphanol uniquely increases kappa(1)-opioid receptor binding in the rat brain. Brain Res Bull.